Telephone system



May 1, 3.945.y c. s. RHOADS TELEPHONE SYSTEM FledMay 5, 1944 2 Sheets-Sheet l IN VEN TOR A TTORNE Y 2 Sheets-Sheet 2 INVENTOR May l, i945., c. s. RHOADS TELEPHONE SYSTEM Filed May 5, 1944 C. .Rl/Loads III 1 Patented May -1, 1945 TELEPHONE SYSTEM Charles Stanley Rhoads, Albany, N. Y., assignor Vto American Telephone and Telegraph Company, a corporation of New York A Application May 5,1944, serial No. 534,272

13 Claims.

ments of the invention are particularly adapted.

for use at unattended yexchanges utilizing machine-switching equipment, which exchanges would be connected to an office having attendants. would `be a community dial oflice which is usually an office serving a small community by lmeans of step-by-step, panel -or cross-bar machineswitching equipment and normally having no attendants. This community dial type -of oiiice An example of .an exchange of this type' Ylice is shown a subscribers set l.

to call a. subscriber .such as the one having subscribers set 2 at the community dial oiiice. The subscriber at the master oice would give the called subscribers number to the operator at the master oice. Let it be assumed that the number, for purposes of illustration, would be 2734. The operator at the `master office through trunk equipment 3 would connect the subscriber to the trunk L1 and trunk equipment `ll lat the community dial oflice would connect this trunk to a selector 5. The selector 5 would return a dial tone to the operator at the master koffice and she would plug dialing equipment into the jack 6 and commence to dial the number 2,734.

` The .first group of two dial impulses would cause would be connected with a so-calle'd master ofnce in another locality which would have :attendants. With the arrangements of the invention, a call originating either at the master ofce or at the community dial office `and intended for a number -at the `community vdial office .may be intercepted by an attendant at the .master office. Arrangements have been provided .in the past for intercepting `a number at -an unattended office, but these arrangements have been relatively expensive and have usually fbeenprovided only in ,exchanges having more than five hun-' dred stations. The arrangements of the-invention are exceedingly simple and inexpensive and hence can be used to provide intercept service at smaller omces where the vexpense of other types of apparatus would be prohibitive. Other objects and features of lthe invention will zapl pear more fully .from the detailed description thereof hereinafter given.

'Ihe invention may be .more fully understood from thev following .description together with the accompanying drawings vin .Figures l and 2 of which are .shown circuit diagrams .embodying a preferred form of the invention and a modifica tion thereof. Like reference characters have been used to denote like parts in both ofthe figures.

In Eig. 1 are shown a. number of trunks, such as Li and Lz, connecting a master oiiice, which is the type of oice which would have attendants, With an unattended office such, for example, as acommunity dial oflice. At the master ofthe switching mechanism of the step-by-step selector to moveto ,its second level of terminals and hunt until an idle trunk, such as 1, was found leading -to the connector 8. The connector 8 for purposes of illustration is shown as .of the step-by-step type and is well-known in the art. .The next group of seven. dial impulses would cause the switching mechanism of the connector 8 to move to the seventh level of terminals, and the succeeding group of three impulses Would cause it to move to the third terminal in that level whereupon the calling .subscriber would be connected to the circuit 9 which would normally lead through a main distributing frame to ythe called subscribers set 2. The fourth group of four dialing impulses is used to contr-ol ringing apparatus which will be referred to in more detail in the description given hereinafter with respect to Fig. 2. However, for the purpose of illustrating this invention, it will be assumed that the called subscribers set 2 has been disconnected at the main distributing frame because ythe subscriber `has moved to another locality or for some other reason. Accordingly, .it would be desirable to intercept this call so that the subscriber 4at the master oice could` be informed that the subscribers set 2 could not be reached. Accordingly, a circuit connection lll is provided `from the circuit 9 to certain apparatus which will function as follows: When a connection is established between circuits 9 and Ill, .ringing current will be Vsent out over the tip and ring conductors of circuits 9 and I0 and will actuate the ringing relay Il. This will close a circuit from ground,l contact of, relay il, conductor i2, winding of relay` I3 to battery and ground. vRelay l3 lwill operate )and lock up over a circuit completed over its inner upper armature and contact, conductor I4, to ground placed on the sleeve of circuit 3 by the connector. The operation of relay I3 will also complete the following circuit: From ground, upper armature and contact of relay I3, conductor I6, winding of relay I'l to battery and gorund. This will operate the relay Il. Before the relay I'I is operated ground is applied to the ring side of the trunk Lz, and the negative pole of battery I8 is connected to the tip side of the trunk Lz. At the vmaster oice the midpoint of a resistance I3 is connected tothe grid of a vacuum tube 20. Due to the connectionof battery I8 to the trunk a negative bias will be applied to the grid of vacuum tube 20 and it will be maintained in an inoperative condition. When relay 'Il operates, however, ground and negative battery i8 are disconnected from the trunk l2, and battery 2I is connected across the trunk L2 in such a manner that the negative bias will be removed from the grid of the tube 20 and it will operate and cause the operation of relay 22. This type of signaling circuit is more completely disclosed in a co-pending application, S. N. 527,914, filed March 24, 1944, in the name of C. S. Rhoads. However, it is understood that any desirable arrangement for signaling over the trunk L2 by means ofthe actuation'of relay Il ymay be utilized. The operation of circuit 22l will operate the signal lamp 23. When the signal lamp 23 operates an operator at the master omce will know that a call has originated either at the master cnice or at the community dial office which must be intercepted because it is for a number not in active use. At the community dial office a certain unlisted number or numbers will be set aside for the intercept service. For example, let it be assumed that the unlisted number 3425 has been set aside for this service. Accordingly, when the lamp 23 lights, the operator will plug into an idle trunk, such as Lz, which will be connected at the community dial olce with a` selector 24. This will send dialing tone back to the operator at the master olice and she will plug dialing equipment into the jack 25 and commence to dial the number 342.5. 'I'he first group of three impulses will cause the switching mechanisml of selector 24 to move to the third level of terminals and select an idle trunk, such as trunk 26, leading to the connector 21. The next groupl of four dial impulses will cause the switching mechanism of the connector to move to the fourth level of terminals and the succeeding group of two dialimpulses will cause it to move to the second terminal thereof, whereupon a connection will be established with the circuit 28. The fourth group of five dialing impulses is used to control ringing apparatus which will be referred to in more detail in the description hereinafter given with` respect to Fig. 2. The tip and ring conductors of circuit 28 are connected througlrcondensers 30 and 3I to the tip and ring conductors of the circuit Ill which in turn are connected to the tip and ring conductors of the circuit 9. This will establish a connection from the operator at themaster ofce back over the trunk L1 to the subscriber having the subscribers set I. When the connection is established with circuit 2B,by connector 21, ground is applied to the sleeve conductor of circuit 28 which will cause relay 32 to operate. The operation of relay `32 at its upper armature and contact will break the previously traced circuit extending over conductor I6 to the relay Il and this will release relay I'l. This will reconnect the negative side of battery I8 to the tip of trunk L2, and ground to the ring side of trunk L2 and replace a negative bias on the grid of tube 20 and cause the tube 20 to become extinguished, whereupon the signal lamp 23 at the master oice will be extinguished. The operation of relay 32 at its upper inner contact will bridge a circuit for the gas-lled discharge tube 33 across the tip and ring conductors of circuits Ill and 9. The voltage of the ringing circuit will discharge the tube 33 and this will trip the ringing current on circuits 9 and I0. The operation of relay 32 will also close over its lower armature and contact a circuit. 34 across the tip and ring conductors of circuit 28. This will trip the ringing current on circuit 23. The tripping of the ringing current will cause connectors 8 and 2l to complete talking paths therein. The operator at the master oiice may now inform the subscriber at the set I that the called subscriber at the setZ cannot be reached by using the number 2734, and give him' the reason therefor.

The arrangements of the invention may also be used to intercept other calls such, for example, as a call for the number 2345 which would result in a connection being established by connector 8 vwith circuit 36. 'I'his circuit would normally extend from the main distributing frame to a subscriber having the subscribers set 3l. However, this set will have been disconnected from circuit 36 at the main distributing frame. Accordingly, a call'coming in for number 2345 would be extended from circuit 36 to circuit I, whereupon, in the same manner as previously described, the signal lamp 23 at the master office would operate and the operator would dial the unlisted number, such at 3425, 'whereupon circuit 28 would be connected to circuits II) and 36 andthe operator would then be connected with the subscriber having the set I at the master oflce. She could then inform the said subscrber that the subscriber having set 3l at the community dial cnice could not be reached for certain reasons. K

A subscriber having a subscribers set 38 at the community dial oice might desire to reach the subscriber having the set 2 by dialing the number 2734.` In a well-known manner, through the line finder 39, the selector 40 and the connector 4I, a connection would be established between the subscriber having set 33 and the circuit 42. This circuit would be connected in multiple with the circuit 9 which, as heretofore pointed out, is connected to the circuit I0. Accordingly, when such a connection is established signal lamp 23 at the master office would light in the same manner as heretofore pointed out, and the operator would then again proceed to dial an unlisted number such as 3425. This would cause the operator to be connectedv to circuit 28 which in turn is connected to circuits I0 and 9, and circuit 9 is connected to circuit 42. The operator would then be connected to the subscriber having thev set 38 and could inform him that the subscriber 2 could vnot be reachedby dialing the number 2734. In a similar'manner if the subscriber having set 38, dialed another number, such as 2345, the operator would be connected to him eventually over circuit 43 and could inform him that she was intercepting his call for certain reasons.

Obviously, while the arrangements of the invention have been shown as being able to'interlrelay 12 would close a circuit over the armature and make contact of relay 13 for the relay 15. This would operate the relay 15 which in turn would cause the relay 15 to .lock up. The next threesucceeding impulses would cause the relays 16 and 16', 1'! and 11* and `90 and 90' to operate and lock up. This would connect ground on the 4sleeve of circuit 28 over the armature and contact of relay 90' to the conductorA 18 and thence through the winding of relay 32 to battery 19.

It would alsol complete a parallel circuit through l the winding of relay 80 which is a slow-operate relay. Accordingly, it will be seen that the relay f 32 will not operate until a denite interval after the ringing code has beenapplied to circuit 2 8 or until the so-called silent period has been reached. 'When relay 32 operates it'closes a tripping circuit 8| over the break contacts and armature of relay 80. This will trip the ringing current on the line 9. As relay 80 is-slow-operate it will not function at the same instant as relay 32 but will operate a short interval thereafter. This Will disconnect the tripping circuit 8i from the line-9 and prevent the operation of the relay 53. As relay 53 is not operated the current transmitted `baclrover the line to the calling station is not reversed and if the calling station happens to be a coin box the coin collect apparatus thereat will not function. The operation of relay 8D in addition to removing thetripping circuit 8| from the line 9, also connects circuit I through condensers and 3l to the circuit 28 thereby establishinga talking path between circuits 9 and'28 and enabling the operator at the master o'ice to inform the calling partythe reason for intercepting the call. The operation of relay 32 will also close a tripping circuit to trip the ringing on circuit 28.

It is pointed out that the arrangements of the jinvention have been disclosed as particularly applicable to a community dial oidce. However, it .is understood that they are not so limited but may be used with other types oi offices. While the arrangements of the invention have been disclosed as embodied in certain specific forms, it is understood that they are capable of embodi* ment in other and widely varied forms without departing from the spirit of the invention as Y defined' by the appended claims.

exchange having two connectors, a telephone line on which incoming calls are to be intercepted connected to a terminal in one of said connectors which may be reached by dialing a designated number, means for connecting said telephone line to a terminal in the other connector which may be reachedby dialing another designated number,l means responsive to the dialingof said rst number for applying ringing vcurrent to said telephone line to cause the transmission of va signal to an attended exchange, and means responsive to the dialing Vof said second numberl for tripping said ringing current.

3. A telephone system including an unattended exchange having two connectors, a telephone line on which incoming calls are to be intercepted connected to a terminal in one of said connectors which may be reacted by dialing a. designated number, means for connecting said telephone line to a terminal in the other'connector which may be reached by dialing another designated numbenmeans responsive to the dialing of said rst member for applying ringing current to said telephone line to cause the transmission of a signal to an attended exchange, and means responsive to the dialing of said second number for bridging a circuit including a gas filled discharge tube across said telephone line to trip said ringing current. I

4. A telephone system including a trunk interconnecting two. exchanges, operators equipment adapted to be connected to said trunk at the first exchange, a connector at the second exchange, a circuit on which incoming calls are to be intercepted connected to one of the terminals of said connector, means responsive to an incoming call on said circuit for transmitting a signal to said operators equipment, a second connector at the secondexchange, and means terconnecting two exchanges, operators equipment adapted to be connected to said trlmk at the rst exchange, a connector at the second exchange, circuits on which incoming calls are to be intercepted connected to certain of the terminals of said connector, means responsive to an incoming call on any of said circuits for transmitting a signal to said operators equipment, a second connector at the second exchange, and means for connecting all of said circuits on which calls are to be intercepted to a Vdesignated one of terminals of said second connector whereby when,4 a connection is established over said trunk between said last mentioned terminal and said operators equipment said calls may be intercepted. n 1

6. A telephone system including trunks interconnecting two exchanges, a calling subscribers set at therst exchange and a called subscribers set at the second exchange, a connector at the second exchange adapted tobe connected to the calling subscribers set, a circuit connected to one of the terminals of said connector. and adapted to be extended to the called subscribers set, a second connector at the second exchange adapted to be connected to operators equipment at the'rst exchange, a circuit extending from one of the terminals of said second connector to said irst mentioned circuit, and means responsive to signaling current transmitted over said rst circuit for transmitting a signal over one of said trunks to the operators equipment at the first exchange.

7. A telephone system including trunks interconnecting two exchanges, a calling subaardige connector and adapted ytobe extended tothe` called subscribers set, a second connector at the. second exchange adapted to, be connected to operators. equipment at, the iirst exchange,

.9, circuit extending from one of the, terminals of said second connector to said firstmentioned circuit, means responsive to signaling current transmitted over said rst circuitfjor transmitting a` signal over one, of Said trunksto the operators equipment at` the liiist exchange, and means. responsive to signaling lcurrent' transmitted over said second' circuitufor causingthe transmission of said signal to.` YCease 8. A telephone system including a trunk interconnecting two exchanges, operators equipment adapted to be connected to said trunk at the first of said exchanges, a connector at the second exchange adapted to be connected to a calling subscriber thereat, a circuit connected to one of the terminals of said connector and adapted to be extended to a called subscriber at said second exchange, a second connector at the second exchange adapted to be connected by said trunk to said operators equipment at said rst exchange, a circuit extending from one of the terminals of said seco-nd connector to said first mentioned circuit, and means respon-v sive to signaling current transmitted over said rst circuit for transmitting a signal over said trunk to said operators equipment at said first exchange. I

9. A telephone system including trunks interconnecting two exchanges, a calling subscribers set at the nrst exchange and a called subscribers set at the second exchange, a connector at the second exchange adapted to be connected to the calling subscribers set, a rst circuit connected to one of the terminals of said iconnector and adapted to be extended to the called subscribers set, means responsive to the establishment of a connection with said first circuit at said connector for applying ringing current to said rst circuit, means responsive to said ringing current for transmitting a signal over one of said trunks to operators equipment at the first exchange, a second connector at the second exchange adapted to be connected to operators equipment at thel rst exchange, a second. circuit extending from one oi the terminals of said second connector to said rst circuit, means responsive to the establishment of a connection with said second circuit at said second connector for applying ringing current to said second circuit, and means operated when a connection is established with'said second circuit at said second connector for tripping the ringing current applied to said first and second circuits.

10. A telephone system including an unattended exchange having two connectors, a telephone line on which incoming calls are to be intercepted connected to a terminal in one of sa1d connectors which terminal may be reached by dialing a designated number, said telephone line having apparatus associated therewith and cperative when the line is seized at said connector for applying ringing current to the line and apparatus for reversing the connection of talklng battery-to the line at the expiration of a certain interval after the ringing current is tripped,

^ means responsive to the application of said ringine, current, to said, line for transmitting a signal to an attended exchange, a normally open circuit rfor connecting; said telephone. line to.. o terminal in the other connector which; terminal, may be reached by dialing another designated number, o. tripping Ciroiiitoonneoted to, said, normally openoircuit, ,means responsive to; the dialing. 0f said second number for closing Seid tripping oir'- ciiit for subsequently disconnecting it from seid normali-r oren ycircuit and, fol? Closing said norm lli-y openA circuit, i, said `lastfmei-itioned means beinefadanted to function vbeiorefseid. apparatus for: reversing the. connection. oitallsiiigbatteri to saidlineliasiiinotioned r 1l. A telephone system including anV unattendedl exchange having two connectors, a telephone line on which incoming calls are tobe intercepted connected toa terminal in-one of said connectors` which terminal may be reached by dialing a designated number, said telephone line having apparatus associated therewith and operative when the line is seized at said connector for applying ringing current to the line and apparatus for reversing the connection of talking battery to the line at the expiration of a certain interval after the ringing current is tripped, means responsive to the application of said ringing current to said line for'transmitting a signal to an attended eX- change, a normally open circuit for connecting said telephone line to a terminal in the other connector which terminal may be reached by dialing another designated number, a slow operate relay, a tripping circuit for tripping the ringing current applied to said line connected to said normally open circuit over the break contacts of said relay, asecond relay, meansr responsive to the dialing of said second number for operating said slow operate relay and said second relay, means controlled by the operation of said second relay for closing said tripping circuit and means controlled by the subsequent operation of said slow operate relay for closing said normally open circuit and for disconnecting the tripping circuit therefrom. l

12. A telephone systems including an unattended exchange having two connectors, a telephone line on which incoming calls are to be intercepted connected to a terminal in one of said connectors which terminal may be reached by dialing a designatednumber, said telephone line having apparatus associated therewith and operative when the line is seized at said connector for applying ringing current to the line and apparatus for reversing the connection of talking battery to the line at the expiration of a certain interval after/the ringing current is tripped, means responsive to the application of said ringing current to said line for transmittingl a signal to an attended exchange, a normally open circuit for connecting said telephone line to a terminal in the other connector which terminal may be reached by dialing another designated number, a slow operate relay, a tripping circuit for tripping the ringing current applied to said line connected to said normally open circuit over the break contacts of said relay, a second relay,`

means responsive to the dialing of said second number for operating after a definite time intery' val said slow operate relay and-said second relay,l means controlled by the operation of said second relay for closing said tripping circuit and means controlled by the subsequent operation of said slow operate relay for closing said normally open circuit and for disconnecting 'the tripping circuit therefrom.

13. A telephone vsystem including an unattended exchange having two connectors, a telephone line on which incoming calls are to be intercepted connected to a terminal in one of said connectors which terminal may be reached by dialing a designated number, said telephone line having apparatus associated therewith and operative whenthe line is seizedV at said connector for applying ringing current to the line and apparatus for reversing the connection of talking battery to the lineat the expiration of a certain interval after the ringing current is tripped, means responusive to the application of said ringing current to said line for transmitting a signal to an attended exchange, a normally open circuit for connecting said telephone line to a tery minal in the other connector which terminal may be reached by dialing another designated number, a' slowoperate relay, a tripping circuit for tripping the ringing current applied to said line connected to said normally open circuit, over the breakl contacts of said relay, a second relay, a chain of countingrelays adapted to be operated successively in response to the dialing of said second number, means controlled by the operationlof the last relay in said chain for operating said slow operate relay and said second relay, means controlled by the operation of said second relay for closing said tripping circuit and means controlled by the subsequent operation of said slow operate relay for closing,r said normally open circuit and for disconnecting the tripping circuit therefrom.

CHARLES STANLEY RHOADS. 

